• Bond, Daniel R.
• Flickinger, M. C.
• Scriven, L. E.
• Schottel, Janet L.
• Lyngberg, O. K.
• Solheid, C.
• Ge, H.
• Laudon, M.
• Gosse, J.
• Fidaleo, M.
• Charaniya, S.
• Polzin, K.

Abstract

<p>Nanoporous, adhesive latex coatings and ink-jet deposited latex microstructures containing concentrated, viable, but nongrowing microorganisms may be useful smart coatings. When rehydrated, these bioactive coatings can be used for multi-step oxidations, reductions, as biosensors, in biofuel cells, or high intensity industrial biocatalysts. Engineering coating microstructure, preservation of microbe viability during drying at ambient temperature and the stability of these coatings following rehydration is investigated in 5 μm to 75 μm thick coatings of microbes concentrated 10² to 10 ³-fold on polyester, metals or electrode substrates. Nanoporosity is essential for preserving microbial viability in dry coatings and bioreactivity following rehydration. Non-toxic (low biocide or biocide-free) latex emulsions contain carbohydrate porogens which vitrify to arrest polymer particle coalescence during film formation generating nanopores. However, the molecular mechanism of how vitrified carbohydrates function as osmoprotectants and preserve microbial viability by formation of glasses in the pore space during film formation is unknown. Coating nanoporosity in hydrated films is estimated by tracer diffusivity and visualized by cryogenic-SEM. Emulsion composition, drying conditions and coating thickness affect microbial viability, substrate adhesion, and coating reactivity following drying, storage and rehydration. The specific reactivity of the entrapped microorganisms can be induced to express enzymes for optimal reactivity prior to coating or the microbes can be "activated" by inducing gene expression following coat drying and rehydration. Laser scanning confocal microscopy is used to investigate spatial gene expression as a function of coating depth and diffusion resistance. Model microbial smart coatings investigated include: an E. coli ionic mercury biosensor, an anaerobic starch hydrolyzing coating of Thermotoga maritima at 80°C, photoreactive coatings of Rhodopseudomonas palustris for anoxic production of hydrogen, coatings of Gluconobacter oxydans which oxidizes D-sorbitol → L-sorbose, and current- generating coatings of Geobactor sulfurreducens on conductive electrode materials.</p>

Topics

• impedance spectroscopy
• microstructure
• pore
• polymer
• scanning electron microscopy
• glass
• glass
• Hydrogen
• diffusivity
• drying
• Mercury
• confocal microscopy
• tracer diffusivity